Watson, along with Francis Crick and Maurice Wilkins, unravelled the double-helix structure and function of deoxyribonucleic acid (DNA) in Britain in 1953. They received the Nobel Prize for medicine in 1962 for their groundbreaking work in genetics.

Now 86, Watson said he planned to donate part of the proceeds of the sale to charities and to support scientific research.

Today, the bidder was revealed as Russia's richest man, metal and telecommunications tycoon Alisher Usmanov, who has an estimated fortune of $15.8 billion (about £10 billion).

Most Britons will also be familiar with him as one of the main shareholders of Arsenal FC.

He said he decided to buy the medal and give it back to Watson when he learned Watson was giving part of the money to charity.

It was the first Nobel medal sold at auction by a living recipient.

Crick died in 2004 and his medal was sold for $2.27 million last year. A letter to his son also sold for a whopping $6 million (£3.8 million), in which he outlined the structure of DNA shortly before the discovery was published.